Heat sensitive pen recorder - with image formed on heat sensitive sheet

摘要

A continuous heat sensitive paper sheet is advanced longitudinally by e.g. a driven roller and a heated pen is pref. moved transversely across the sheet by a driven wire. The drive speeds of the pen and the paper are compared to give a signal which is dependent on the relative speed between the pen and the paper. The signal is used to control the energy supplied to the pen. Impulse generators provide pulsed signals whose frequency depends on the speeds of the pen and paper and a mono-stable multivibrator produces pulsed energy outputs dependent on the mean of the outputs frequency. The pen may be of silicone having P or N type phosphorous or boron dispersions forming a heatable conductive tip or a ceramic having a conductive coating on its tip. The paper sheet may have additive layers so that it can change colour in the region of the image. a fixed visible image is produced immediately. No replenishing with ink or subsequent fixing etc. is required as with conventional machines.